Abel O. Olorunnisola

Briquetting of rattan furniture waste

This paper presents the findings of a study involving experimental production of briquettes from chopped rattan strands mixed with cassava starch paste. Samples of rattan strands of mixed species (Laccosperma secundiforum and Eresmopatha macrocarpa) were collected from a furniture workshop in Ibadan, Oyo State, Nigeria. The strands, having an average moisture content of 12% and an average dimension of 630 mm (length) by 4.0 mm (width) and 1.8 mm (thickness), were reduced to 25 mm (length) by 4.0 mm (width) and 1.8 mm (thickness) particles by manual shearing. They were subsequently mixed with cassava starch at six proportions by weight, i.e. 50%, 100%, 150%, 200%, 250%, and 300%. It was observed that the minimum proportion by weight of cassava starch required for briquette formation was 200%. Compression experiments were performed using a simple tabletop closed - end die piston press fitted with both a pressure and a dial gauge. Four levels of pressure application: 3.5 N/mm2, 7.0 N/mm2, 10 N/mm2 and 14 N/mm2, and two loading duration (dwell times), 3 min and 5 min, respectively were employed. Results obtained showed that the minimum pressure required for briquette formation was 14 MPa. The specific energy required to form the rattan strand briquettes at 200%, 250% and 300% cassava starch content levels was 8 J/t, 9.3 J/t and 11.1 J/t, respectively. A reciprocal relationship between binder content and relaxed density was observed. All the expansion (minimal in all cases) of the briquettes took place within 30 min. It was concluded that stable briquettes could be formed from rattan strands mixed with cassava starch paste.

Mechanical Properties of Wood

This chapter is a follow up on the previous one on the anatomical and physical properties of hardwoods in general. In this chapter, therefore, the reader is introduced to the mechanical properties of wood, i.e., those properties of wood that usually require mechanical stress for their determination (excluding non-destructive test methods). These include the strength of wood as affected by rate and duration of loading, mode and direction of applied stress, moisture content, density, and exposure to either low or high temperature, and/or chemicals. Some numerical examples are treated using Microsoft Excel. A simple FORTRAN code for solving the popular Hankinson formula is also presented.

Strength properties and potential uses of rattan–cement composites

Wood–cement particleboard (WCP) was produced from rattan (Laccosperma secundiflorum) particles. Contrary to conventional practice, the boards were fabricated in the laboratory without pressure application. The effects of rattan particle size and content on the density and bending and compressive strength properties of the boards were investigated. The boards were produced using two rattan particle sizes, i.e., those passing through a 0.85 mm sieve but retained on 0.6 mm sieve, and a 50 : 50 mixture (by weight) of particles retained on 1.2 mm and 0.85 mm sieves, three cement–rattan mixing ratios (by weight of cement) of 1 : 0.11, 1 : 0.19 and 1 : 0.25 respectively, i.e., rattan contents of 10, 15 and 20%. Board density ranged between 764 and 1340 kg/m3, indicating that the composite is a lightweight concrete. The mean modulus of elasticity (MOE = 130.2−2830.7 N/mm2) and modulus of rupture (MOR = 0.8 and 5.2 N/mm2) of the boards decreased with increasing rattan particle size and content. The mean compressive strength of boards (1.3−22.0 N/mm2) also decreased with decreasing board density. Cement–rattan mixing ratio, rattan particle size and the interaction of both variables had significant effects on the density, modulus of rupture and the compressive strength of the composites. The density and the compressive strength properties of the composites suggest that they could find suitable application in the production of insulation boards and bricks (with the addition of sand), for erection of bearing walls in low-rise buildings.

Hydration characteristics of cement-bonded composites made from rattan cane and coconut husk

This work examines the effect of CaCl 2 on the hydration of rattan ( Laccosperma secundiflorum ) and coconut ( Cocos nucifera ) husk particles mixed with Portland cement. Hydration tests were conducted in sealed thermally insulated containers using an aggregate/cement/water ratio of 15 g : 200 g : 90.5 ml. CaCl 2 was added at four concentrations (by weight of cement): 0 (control) 1, 2 and 3% for the rattan and coconut husk particles, and at 0 (control) and 3% for a 50:50 mixture (by weight) of rattan and coconut husk. Hydration temperature was monitored on-line over a period of 23 h. The compatibility of both aggregates and their 50:50 mixture with Portland cement was assessed using the parameters of time to maximum hydration temperature, maximum hydration temperature, inhibitory index, and rate of heat generation. Findings showed that without CaCl 2 both aggregates exhibited relatively low level of compatibility with Portland cement, with the rattan particles exhibiting relatively higher degree of inhibition. The addition resulted in reduced setting time (about 60%), increased hydration temperature (50–80%), lower inhibitory index and higher rate of heat generation in all the aggregate/cement mixtures. Recommendations for further research include the identification of the cement-inhibitory chemicals present in coconut husk and rattan and investigations on the mechanism of CaCl 2 interaction with rattan/cement and coconut husk/cement systems.

Biogas as an alternative energy source and a waste management strategy in Northern Ethiopia

ABSTRACT The consumption of fuel wood and charcoal in Ethiopia continues to increase as there is limited or no access to modern energy sources in the majority of rural areas, and most households cannot afford, even if they have access to, modern energy sources. This has resulted in environmental degradations in various forms. Harnessing biogas energy at household level can be a sustainable energy option for low income households. Based on primary data collected using a household survey and the use of propensity score matching model, this study analyses the contribution of biogas energy to reduction in firewood and charcoal consumption of households and its role in the management of cattle dung and human excreta in Ofla district, Ethiopia. The empirical findings show that the fuel wood and charcoal consumptions of biogas adopter households were on average reduced by 143.55 kg hh−1 month−1 (45% reduction) and 16 kg hh−1 month−1 (50.9% reduction) respectively compared to their non-adopter counterparts. Each biogas adopter household utilises about 2.1 kg day−1, 7.2 kg day−1 and 20 kg day−1 of wet faeces, urine and cattle dung respectively via anaerobic digestion which would otherwise have been unsafely discharged into the local environment.

A Review of the Basic Theory of Structures

This chapter presents a review of the basic theory of structures. It starts by presenting a simple definition and function of structures and proceeds to discussions on the force actions on structural elements; the two broad sub-divisions of structures, i.e., mass structures which resist applied loads by virtue of their weight and framed structures which resist applied loads by virtue of their geometry, the basic elements of a framed structure and types of joints in a framed structure; the basic properties of sections is also treated, and a Microsoft Excel template for computing the area, section modulus and moment of inertia of pieces of lumber is presented.

Structural Load Computations

This chapter opens with a discussion on the main objective of structural design, which is to produce a structure capable of resisting all applied loads without failure during its intended life. It is noted that if actual applied loads exceed design specifications, the structure may fail, with potentially serious consequences. Hence, structural load determination is very essential, and such loads, which may be divided into two categories, i.e. vertical (gravity) loads and lateral forces, are discussed. In doing this, vertical loads are further categorized into two, i.e. dead loads which are permanent, and live loads which tend to fluctuate with time. A Microsoft Excel template for computing the dead loads is presented as part of the worked examples provided.

Uses of Wood and Wood Products in Construction

This chapter is focused on the different uses of wood and wood products for structural purposes. It highlights the factors that favour this mode of wood utilisation. It also discusses the emergence of different wood products as structural materials; advantages and disadvantages of structural utilization of wood products in different forms; lumber sizes and grades employed across Africa; and presents a simple method of obtaining approximate working-stress data for indigenous species for which design values are not available in existing design codes, based on their densities. The properties and various uses of wood-based panel products, engineered wood products, wood–cement and wood–plastic composite panels are also discussed.

Design of Wood Connections

This chapter is a treatise on wood connections, with particular reference to mechanical as opposed to adhesive and other forms of connecting wood to itself and/or other materials, though a passing reference is made to traditional method of connecting wood members without the use of metal fasteners and wood adhesives. Topics addressed include types of joint loads, i.e. shear connections, also known as laterally loaded connections, in which the load is applied perpendicular to the length of the fastener, and withdrawal loading in which the load is applied parallel to the length of the fastener. Different types of wood fasteners including nails, bolts, lag bolts, wood screws, split rings, shear plates and nailed gusset plates are also discussed. However, given its wide use and relative popularity in Africa, many more worked examples are presented on nailed joints than the other joints. The core issues of nail penetration and spacing are also discussed.

Design of Built-Up Wooden Columns

This chapter is a follow-up to the previous one that delt with the design of solid timber columns. Here, the design and fabrication of two common types of built-up wooden columns, i.e. spaced and glulam columns, are treated. Spaced columns are defined as two or more solid rectangular members joined at the ends to ensure that the individual member acts as a single unit, while glulam is typically made up of rectangular members glued together from smaller pieces of wood, either in straight or curved form, with the grain of all the laminations essentially parallel to the length of the member. Design- and fabrication-related issues treated include spacer and end block provisions for spaced columns, production of glulam members by horizontal and vertical lamination, advantages of glulam over solid-sawn wood construction, and the design criteria for both spaced and glulam columns. Worked examples including computer codes are also presented.